WO2017162647A1

WO2017162647A1 - Device and method for producing an optical pattern from pixels in an image plane

Info

Publication number: WO2017162647A1
Application number: PCT/EP2017/056658
Authority: WO
Inventors: Peter Dürr; Alexander Mai
Original assignee: Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V.
Priority date: 2016-03-22
Filing date: 2017-03-21
Publication date: 2017-09-28
Also published as: US11067953B2; DE102016204703A1; US20190011885A1; DE102016204703B4

Abstract

The invention relate to a device for producing an optical pattern from pixels in an image plane, comprising: a control apparatus for controlling the production of the optical pattern; a micromirror array for reflecting light beams, which hit the micromirror array over an area, wherein the micromirror array has a plurality of micromirrors, each of which can be tilted by the control apparatus at least about a first axis such that a direction of a center-of-gravity beam of the light beams reflected at the particular micromirror can be set; a lighting apparatus controllable by the control apparatus for producing the light beams, which is designed in such a way that the light beams are at least partially planarly coherent; a focusing apparatus for focusing the light beams reflected at the plurality of micromirrors of the micromirror array onto the image plane; wherein the control apparatus is designed to control one or more micromirror groups formed by several micromirrors of the plurality of micromirrors in such a way that the center-of-gravity beams reflected at the micromirrors of one of the micromirror groups meet in the image plane and that optical path lengths of the center-of-gravity beams reflected at the micromirrors of the particular micromirror group from the lighting apparatus to the image plane are equal or differ by an integer multiple of a wavelength of the light beams in order to thus produce one of the pixels.

Description

Apparatus and method for generating an optical pattern

Biidpunkte in a picture plane

description

This invention relates to an apparatus and method for generating a programmable optical pattern.

A large number of devices for producing optical patterns are already known. In a classic slide projector, e.g. Light is absorbed by the slide wherever the intensity in the desired pattern should be small. This works with high resolution (number of distinguishable pixels), but the light output can - depending on the image content - be quite small due to the absorption, and a pattern change requires a complete change of the slide. In addition to the unwanted loss of light itself, the heating of the slide by the absorption can lead to problems.

A kind of further development of the slide projector are the so-called beamer, in which instead of the slide a freely programmable area light modulator (SLM) defines the pattern. The surface light modulator can either be micromechanical (with micromirrors, especially the DLP technology from Texas Instruments) or liquid crystals (LCD, LCoS). It allows the computer-aided generation of a wide variety of optical patterns without the need for previous production of individual slides. In addition, the absorption of the light is advantageously spatially separated from the area light modulator. However, it remains unfavorable that low-intensity sites can only be achieved by absorbing the (expensive) radiation. This is particularly unfavorable if the desired patterns are to have a large proportion of dark spots and only small areas with particularly high peak intensities. This comes z. In optical material processing, e.g. by melting or ablation.

In order to avoid light losses through absorption, pattern generation by means of diffractive optical elements (DOE) already exists in the prior art. By such a diffractive optical element of the incident Modulated light beam in its phase so that it effectively, according to the desired pattern, is split into a plurality of partial beams, which z. 6. is described in document [1]. The pattern to be generated appears here in the far field or in the focal plane of a lens when the incident on the diffractive optical element radiation is a plane wave (alternatively, the illumination can also be done with convergent or divergent light, the image is then produced elsewhere, which is immaterial here). Unlike a slide, the diffractive optical element is not actually imaged. In the simplest case, the diffractive optical element consists of a one-sided structured transparent or also reflecting plate. In this case, however, a corresponding new diffractive optical element must be produced for the projection of another pattern. This principle of pattern generation is described, for. B. applied in the illumination beam path of current semiconductor lithography machines.

The pattern generation according to the principle of diffractive optical elements can be made quickly variable with programmable surface light modulators, which z. As disclosed in document [2]. In principle, phase-shifting surface light modulators, which may, for example, have micromirrors or liquid crystals, are suitable for this purpose. The disadvantage here is that a diffractive optical element for a good image quality with regard to the resolution and the illuminated angle range requires extremely many and extremely small pixels whose dimensions are close to the wavelength of the light. While this is easy to achieve with solid, etched diffractive optical elements, the extreme reduction of the active pixels of a surface light modulator is technically much more difficult and expensive. In addition, control data must also be calculated for all these pixels and transmitted to the area light modulator, which also means a great deal of effort.

Another way go therefore structures with surface light modulators, which pursue an incoherent pattern generation according to the beam-steering principle, which z. B. by document [3], there specifically Figure 10, is disclosed. Such surface light modulators have in two dimensions tiltable micromirrors whose deflection is often referred to as a tip tilt function and which are much larger than the used wavelength of light. Each individual micromirror thus essentially reflects those partial beams of the incident light which fall on it, essentially according to the principle of angles of incidence equal to angles of incidence. When illuminated with a plane wave, the desired light pattern is then formed by suitable deflection of all micromirrors from the respective partial beams in the far field or in the focus of a lens. This method is principally characterized in that the partial beams, which emanate from different micromirrors but contribute to a common pixel, overlay incoherently.

This structure, like a comparable structure with a diffractive optical element, has the property that the entire light reflected by the surface light modulator can be used. It is very advantageous in this case that substantially fewer pixels are required than in the case of a surface light modulator having a diffractive optical element, so that much less drive data also has to be calculated and transmitted. However, this structure also has the disadvantage that the diffraction at the individual micromirrors delimits the resolution and the sharpness of the image. In other words, the diameter of each pixel of the partial beams in the image plane can not become smaller than that caused by the diffraction at the individual micromirror. For a very good image quality, especially in terms of resolution and sharpness, therefore, very large micromirrors are required, which in turn can be produced in the current MEMS processes only with great effort in large micromirror arrays for many independent pixels. In addition, the moment of inertia of large micromirrors increases with a high power of lateral dimensions, the exact value of the power depending on the scaling of the mirror thickness, which must be increased for acceptable planarity. With limited drive voltages and therefore forces, large micromirrors can only be moved much slower than smaller ones

The object of the present invention is to provide an improved apparatus for generating a two-dimensional optical pattern of pixels in an image plane. The object is achieved by an apparatus for producing a two-dimensional optical pattern of pixels in an image plane, comprising the following features: a control device for controlling the generation of the optical pattern; a micromirror array for reflecting light beams incident flatly on the micromirror array, the micromirror array having a plurality of micromirrors each tiltable by the control means at least about a first axis such that a direction of a centroid beam reflects that of the respective micromirror Light rays is adjustable; an illumination device controllable by the control device for generating the light rays, which is designed so that the light rays are at least partially coherent surface; focusing means for focusing the light beams reflected at the plurality of micromirrors of the micromirror array onto the image plane; wherein the control device is designed to control one or more micromirror groups formed from a plurality of micromirrors of the plurality of micromirrors, such that the centroid beams reflected at the micromirrors of one of the micromirror groups meet in the image plane, and optical path lengths at the micromirrors of the respective micromirrors Micromirror group reflected focal rays from the lighting device to the image plane are the same or differ by an integer multiple of a wavelength of the light beams, so as to produce a pixel of the pixels.

The control device may in particular be a digital electronic control device, in particular a computer.

A centroid ray of the light rays reflected at a micromirror is understood to mean that light ray which is reflected at the center of gravity of the mirror surface of the respective micromirror. At a right-angled mirror surface, the center of gravity is defined, for example, by the crossing point of the diagonal of the mirror surface.

The illumination device is designed such that the generated light beams are substantially coherent at least in the spatial region of one of the micromirror groups.

The focusing device can be arranged between the micromirror array and the image plane or between the illumination device and the micromirror array.

The solution to the above object is based on the above-described beam steering structure, wherein at least partially spatially coherent light beams are used, which interfere in the image plane, wherein the phases of the interfering center of gravity beams are controlled.

The essential difference between the device according to the invention and the device known from document [3] is that at least partially coherent light is used to interfere in the image plane, the phases of the interfering centroid beams being set by adjusting their optical path lengths ,

In the device according to the invention, the micromirrors of the respective micromirror group are controlled in such a way that the substantially coherent light beams of the micromirrors of the micromirror group are structurally superimposed so as to produce a pixel. For this purpose, the micromirrors of the respective micromirror group are tilted in such a way that, on the one hand, they reflect on the micromirrors of one of the micromirror groups

Focusing rays in the image plane in a center of the pixel meet and that the optical path lengths of the reflected at the micromirrors of the respective micromirror focus beams from the lighting device to the image plane are the same or differ by an integer multiple of a wavelength of the light beams. By adjusting the optical path lengths, it is achieved that the heavy-weight beams arriving at the center of the center point have the same phase position. This avoids that the coherent light beams produce unwanted diffraction patterns, which would cause a division of the pixel into several subpixels, and thus increase the image noise.

For each pixel in the image plane, according to the invention, the micromirrors of a micromirror group are controlled in such a way that the centroid rays reflected at the micromirrors of one of the micromirror groups meet exactly in the middle of the desired pixel. The control device can be designed such that the micromirrors of a micromirror group for generating a pixel are aligned in parallel in order to ensure that the centroid beams reflected at the micromirrors of one of the micromirror groups meet exactly in the middle of the desired image point , The spatial position of the micromirrors involved is calculated and set such that the optical path length of all these center-of-gravity beams from the illumination device to the image plane is the same or differs by an integer multiple of the wavelength of light used. This can be accurate to a small fraction of the wavelength of light used, e.g. 5%, better 1%.

This means that all centroid rays of a micromirror group structurally interfere, which produces a correspondingly high intensity here. In the vicinity of this point, other phase relationships of the light beams reflected at the respective micromirror inevitably result, which automatically result in a steep drop in intensity and thus a sharp image point. With good micromirror quality and precise control, the diameter of this pixel can be as small as corresponds to the diffraction on a single micromirror of the size of the entire micromirror group used. Thus, a micromirror array of, for example, 16 micromirrors can produce a pixel 1/16 of that area which would result from a single one of these micromirrors. The intensity in the center of this pixel is thereby 256 times (= 16 ² ) larger. In contrast, an incoherent superimposition of the reflected light rays in a micromirror group of 16 micromirrors results in an image point with the original latitude and longitude and only 16 times higher intensity.

The micromirrors of one of the micromirror groups are preferably arranged in the manner of a square matrix (n × n matrix). In this case, the same sharpness is obtained for the longitudinal direction and the width direction of the pixel. In principle, however, the micromirrors of one of the micromirror groups can be arranged in the manner of any desired m × n matrix. In this case, the micromirrors of one of the micromirror groups can be adjusted independently of the micromirrors of the other micromirror groups so as to be able to produce different pixels.

The invention enables the projection of an optical pattern directly from a computer without individual preparation of auxiliary elements, such. As masks or diffractive optical elements is determined. The micromirror array also allows the positioning of the pixels and the production of the phase equality of the centroid rays of the pixels. The pattern generation principle of the device according to the invention is not based on the absorption of the already generated light, therefore offers a high luminous efficacy and has a high resolution and precision of pattern reproduction.

The invention is particularly suitable for applications in which the sharpest possible bright points of light in a dark environment are needed, which can be freely positioned and set in their intensity. Here, in particular, the material processing should be mentioned, especially the ablation, but also thermal treatment up to the melting of the surface of a workpiece. The chemical influence of a workpiece or photoresist is conceivable, such. B. in lithography. The use in other devices for pattern generation is also possible.

In one exemplary embodiment of the device according to the invention, the individual micromirrors of the micromirror array can be tilted about exactly one first axis and otherwise fixed. In this case, the micromirrors of a row of the micromirror array can be tilted about a common first axis which is aligned parallel to the line. The micromirrors of the other rows can each be tilted about a further common first axis, wherein the first axes of the different rows can each be aligned parallel to one another. In this case, the micromirrors of a micromirror group can be tiltable about the respective first axis independently of the micromirrors of the other micromirror groups, so as to simultaneously generate a plurality of pixels offset transversely to the first axis. Lines and columns of the micromirror array can be exchanged mutatis mutandis. If the micromirrors can only be tilted about a first axis, the generation of one-dimensional optical patterns is possible.

The condition of the phase equality of the centroid beams in a micromirror group, which are used together for one pixel, can, however, only be fulfilled for discrete pixels, the spacing of the possible pixels depending on the grid of the micromirror array. Thus, the continuum of possible pixels in the image plane is limited to the discrete grid of the diffraction orders of the micromirror array. The advantage of this embodiment, however, is that the amount of control data required for the micromirror array is comparatively low.

The restriction to a given grid of possible pixels may initially appear very unfavorable, but an application for pattern generation may be useful. So z. For example, individual markings on products can be made by ablation. Here a high peak intensity is important, whereby the optical pattern can also be recognized well if the individual pixels are clearly separated from each other. Other embodiments without this limitation will be disclosed below.

According to an advantageous development of the invention, a length of the micromirrors and / or a width of the micromirrors is at least 5 times, preferably at least 10 times, and particularly preferably 20 times, the wavelength of the light beams. In this way it can be ensured that at the individual micromirrors a deflection of the light beams takes place according to the equation angle of incidence = angle of failure. moreover Thus, the number of required micromirrors can be kept small, so that the amount of required control data can be kept small.

According to an expedient development of the invention, the control device is designed to form one of the micromirror groups such that one of the micromirror groups is formed from adjacent micromirrors of the plurality of micromirrors. This makes it possible to ensure that the light beams incident on the micromirrors of the micromirror group thus formed are particularly coherent, so that particularly sharply delimited pixels can be generated. Adjacent are micromirrors when no other micromirror is between the mirrors considered.

According to a preferred embodiment of the invention, the control device for controlling the micromirror groups is designed such that two adjacent or overlapping pixels (BP) of the pixels (BP) can be generated by two non-adjacent micromirror groups of the micromirror groups. As a result, it is possible that in addition to the particularly sharply delimited pixels, pixels with softer transitions can be generated, since the coherence of the light rays incident on the micromirrors of the respective micromirror group decreases in practice if the micromirror groups are spaced apart spatially.

Micromirror groups are adjacent when there is no micromirror of another micromirror group between the micromirror groups under consideration. Micromirror groups are then not adjacent to each other, who are micromirrors of another micromirror group between the considered micromirror groups. When using partially coherent illumination, adjacent or overlapping pixels in the image plane can be formed by non-adjacent micromirror groups whose spacing is above the spatial coherence length. Thus, in addition to the generation of particularly sharp pixels, it is possible to produce broader light distributions with softer transitions by selecting the light beams used to produce the one adjacent pixel to be incoherent in the Relative to the light rays, which are used to generate the other adjacent pixel.

According to an expedient development of the invention, the control device is designed to control an intensity of the illumination device. Since the device according to the invention uses the entire light reflected by the micromirror array, it makes sense if the intensity of the illumination device can be changed rapidly. Then, just as much light can be generated at any one time as is currently needed according to the optical pattern to be generated. If the illumination device does not allow a sufficiently fast modulation, an absorber can alternatively or additionally be used, which is designed, for example, such that it is irradiated at large micromirror angles and thereby absorbs light. According to a preferred development of the invention, the micromirrors are each tiltable by the control device additionally about a second axis, which runs transversely to the first axis, so that the direction of the center of gravity beam of the light rays reflected at the respective micromirror is two-dimensionally adjustable. In this case, the micromirrors of a column of the micromirror array can be tiltable about a common second axis, which is aligned parallel to a column of the micromirror array. The micromirrors of the other column can each be tilted independently of each other about a further common second axis, wherein the second axes of the different columns can each be aligned parallel to one another. In this case, the micromirrors of a micromirror group can be tiltable about the second axes independently of the micromirrors of the other micromirror groups so as to simultaneously generate a plurality of image points in order to simultaneously generate a plurality of pixels offset transversely to the respective second axis. Lines and columns of the micro mirror array can be exchanged mutatis mutandis. If the micro mirrors can be tilted about a first axis and a second axis, the generation of two-dimensional optical patterns is possible.

According to an expedient development of the invention, the control device is designed to form one of the micromirror groups such that one of the micromirror groups consists of two-dimensionally arranged micromirror groups. is formed by the multiplicity of micromirrors. In this way, a microspile group could be formed whose micromirrors are arranged particularly close to each other, so that the light rays incident thereon are particularly coherent, so that particularly sharp image points can be generated.

According to an expedient development of the invention, the micromirrors are each displaceable by the control device along a stroke direction, which runs transversely to a mirror surface of the respective micromirror, so that the optical path length of the center of gravity beam reflected at the respective micromirror can be changed.

If this feature is provided in an embodiment in which the micromirrors are tiltable just about the first axis, then the pixels can be continuously generated on a line since the phase condition for each point of the line is adjusted by adjusting the Hubs can be guaranteed. In this case, in particular in applications which have different requirements for the two coordinate axes in the image plane, the outlay in terms of production and, above all, for the calibration and the activation of the micromirror array can be reduced.

If this feature is provided in an embodiment in which the micromirrors are tiltable about the first axis and about the second axis, then it is possible to image pixels at any location in the image plane, ie without observing a grid to generate since the phasing condition for each location of the image plane can be ensured by adjusting the stroke.

According to an expedient development of the invention, the control device is designed to control a displacement device which is designed to displace an irradiable region in a displacement direction relative to an object to be irradiated.

An area which can be irradiated can be understood to be that area in which an optical pattern can be generated in one operation or with one light pulse. Shape and size of the irradiated area are dependent on the degrees of freedom of the micromirrors, the focal length of the focusing device and the possible Abienkwinkein the micromirror. If areas outside the irradiable area are to be irradiated, this can be achieved by relative displacement of the object to be irradiated in relation to the area which can be irradiated and by multiple light pulses, so that a larger total area that can be irradiated is produced. This can also be referred to as stitching of optical partial patterns.

According to a preferred embodiment of the invention, the displacement device is designed as a mechanical displacement device. The mechanical displacement device can be designed such that either the optical pattern or the object to be irradiated or both are moved.

According to an advantageous development of the invention, the displacement device is designed as an optical displacement device. In this case, the optical displacement device can in particular have one or more tiltable mirrors and / or one or more rotating polygon mirrors.

According to a preferred embodiment of the invention, the displacement device is designed so that the displacement direction extends obliquely to a dot raster of the optical pattern. In this way, it is possible by means of a shift to move a dot matrix of possible pixels over the object to be irradiated in such a way that an area which can be irradiated completely covers the object to be irradiated.

In a further aspect, the object is achieved by a method for generating an optical pattern from pixels in an image plane, comprising the steps of: controlling the generation of the optical pattern by means of a control device;

Reflecting light rays incident on a micromirror array in a planar manner, wherein the micromirror array has a multiplicity of micromirrors which are each at least about a first axis by the control device be tilted to adjust a direction of a centroid ray of the light rays reflected at the respective micromirror;

Generating the light beams by means of an illumination device controlled by the control device, the light beams being generated in such a way that they are at least partially spatially coherent;

Focusing the light beams reflected at the plurality of micromirrors of the micromirror array onto the image plane by a focusing device;

Use of the control device for controlling a micromirror group formed from a plurality of micromirrors of the plurality of micromirrors, such that the centroid beams reflected at the micromirrors of the micromirror group meet in the image plane, and optical path lengths of the centroid beams reflected at the micromirrors of the micromirror group of the illumination device are the same up to the image plane or differ by an integer multiple of a wavelength of the light beams, so as to produce a pixel of the pixels. Advantages and possible further development are described with reference to the device according to the invention.

In the following, the present invention and its advantages will be described in more detail with reference to figures. Show it:

1 shows a first embodiment of a device according to the invention in a schematic representation in an x-y plane;

FIG. 2 shows a detailed view of the first exemplary embodiment of the device according to the invention in a schematic representation in a z-y plane;

Figure 3 is a diagram illustrating the operation of the first

Embodiment of the device according to the invention; FIG. 4 shows a detailed view of a second exemplary embodiment of the device according to the invention in a schematic representation in a zy plane; FIG. 5 shows a detailed view of a third exemplary embodiment of the device according to the invention in a schematic illustration in an xy plane; a diagram illustrating the operation of the third embodiment of the device according to the invention; a partial view of a fourth embodiment of the inventive device in a schematic representation in an xy plane; a partial view of a fifth embodiment of the inventive device in a schematic representation in an xy plane; a detailed view of a development of the second exemplary embodiment of the device according to the invention in a schematic representation; a detailed view of a development of the third embodiment of the device according to the invention in a schematic representation; a detailed view of a development of the third embodiment of the device according to the invention in a schematic representation; and a detailed view of a development of the third embodiment of the device according to the invention in a schematic representation. Identical or similar elements or elements with the same or equivalent function are provided with the same or similar reference symbols in the following place. In the following description, embodiments having a plurality of features of the present invention will be described in detail to provide a better understanding of the invention. It should be noted, however, that the present invention may be practiced by omitting some of the features described. It should also be pointed out that the features shown in various exemplary embodiments can also be combined in other ways, unless this is expressly excluded or would lead to contradictions.

Figure 1 shows a first embodiment of an inventive device 1 in a schematic representation. The device for generating an optical pattern OM from pixels BP in an image plane BE comprises the following features: a control device 2 for controlling the generation of the optical pattern OM; a micromirror array 3 for reflecting light beams LS which are incident flatly on the micromirror array 3, the micromirror array 3 having a multiplicity of micromirrors 4 which can be tilted by the control device 2 at least about a first axis EA, so that a Direction of a centroid beam SST of the respective micro mirror 4 reflected light beams LS is adjustable; a lighting device 5 controllable by the control device 2 for generating the light beams LS, which is designed such that the light beams LS are at least partially spatially coherent; a focusing device 6 for focusing the light beams LS reflected at the plurality of micromirrors 4 of the micromirror array 3 onto the image plane BE; wherein the control device 2 is designed to control one or more micromirror groups 7 formed from a plurality of micromirrors 4 of the plurality of micromirrors 4 such that the focus beams SST reflected at the micromirrors 4 of one of the micromirror groups 7 meet in the image plane BE and that optical path lengths are at Focusing beams SST reflected from the illumination device 5 to the image plane BE are different from the micromirrors 4 of the respective micro-filter group 7 or differ by an integer multiple of a wavelength of the light beams LS, so as to produce a pixel BP of the pixels BP.

In the view of FIG. 1, only one column of the micromirror array 3 is visible, for example four micromirrors 4.1 to 4.4. Another 3 columns of the micromirror array 3 are hidden. However, this is to be understood as an example insofar as substantially more gaps, each with significantly more micromirrors 4, can be provided in practice.

Of the light beams LS, only the centroid beam SST1, which is reflected at the micromirrors 4.1, centroid beam SST2, which is reflected at the micromirror 4.2, centroid beam SST3, which is reflected at the micromirror 4.3, and centroid beam SST 4, which is at the micromirror 4.4 is reflected, shown.

In this case, the pixel BP is generated by an interfering superimposition of the coherent gravity spot beams SST1 to SST4.

The control device 2 is designed to control the micromirror array 3 by means of control data STM and to control the illumination device 5 by means of control data STB.

According to an advantageous development of the invention, the control device 2 is designed to control an intensity of the illumination device 5. Since the device 1 according to the invention uses the entire light reflected by the micro mirror array 3, it makes sense if the intensity of the lighting device 5 can be changed rapidly. Then just as much light LS can be generated at any time as generating optical pattern OM is currently used. If the lighting device 5 does not allow a sufficiently fast modulation, alternatively or additionally an absorber can be used which, for example, is designed such that it is irradiated at large micromirror angles and thereby absorbs light LS.

In a further aspect, the invention relates to a method for producing an optical pattern OM from pixels BP in an image plane BE, which comprises the following steps:

Controlling the generation of the optical pattern OM by means of a control device 2;

Reflecting light beams LS, which surface area on a micromirror array 3, the micromirror array 3 having a plurality of micromirrors 4, which are each tilted by the control device 2 at least about a first axis EA to a direction of a centroid beam SST of the respective micromirror 4 to adjust reflected light beams LS;

Generating the light beams LS by means of a lighting device 5 controlled by the control device 2, the light beams LS being generated in such a way that they are at least partially spatially coherent; Focusing the light beams LS reflected at the plurality of micromirrors 4 of the micromirror array 3 onto the image plane BE through a focusing device 6;

Use of the control device 2 for controlling a micromirror group 7 formed from a plurality of micromirrors 4 of the plurality of micromirrors 4, such that the centroid beams 7 reflected at the micromirrors 4 of the micromirror group 7 meet in the image plane BE, and optical path lengths corresponding to the Micromirrors 4 of the micromirror group 7 reflected focus beams SST from the illumination device 5 to the image plane BE are equal to or an integral multiple of a Distinguish wavelength of the light beams LS, so as to generate a pixel BP of the pixels BP.

Figure 2 shows an Oetailansicht of the first embodiment of the inventive device 1 in a schematic representation.

In the first exemplary embodiment of the device 1 according to the invention, the individual micromirrors 4 of the micromirror array 3 can be tilted by exactly one first axis EA and otherwise fixed. In this case, the micromirrors 4.1, 4.5, 4.9, 4.13 of a first row of the micromirror array 3 can be tiltable about a first common first axis EA1, but independently of one another, which is aligned parallel to the first row. The micromirrors 4.2, 4.6, 4.10, 4.14 of the second row are each independently tiltable about a second common first axis EA2, the micromirrors 4.3, 4.7, 4.11, 4.15 of the third row are around a third common first axis EA3 tilt independently and the micromirrors 4.4, 4.8, 4.12, 4.16 of the fourth row are tilted independently of each other about a fourth common first axis EA4, wherein the first axes EA1-EA4 of the different rows can each be aligned parallel to each other.

In this case, the micromirror group 7.1 can be formed from the micromirrors 4.1, 4.2, 4.3 and 4.4, which are each arranged in the same column of the micromirror array 3. The micromirror group 7.2 can be formed from the micromirrors 4.5, 4.6, 4.7 and 4.8, which are each arranged in the same column of the micromirror array 3; the micromirror group 7.3 can be formed from the micromirrors 4.9, 4.10, 4.11 and 4.12, which respectively are formed in the same column of the micromirror array 3, and the micromirror group 7.4 can be formed of micromirrors 4.13, 4.14, 4.15 and 4.16, which are respectively arranged in the same column of the micromirror array 3. The micromirror groups are thus arranged, for example, in the manner of a 4 × 1 matrix.

If the micromirrors 4 can only be tilted about a first axis EA, it is possible to produce one-dimensional optical patterns. However, the condition of the phase equality of the centroid rays in a microreggio group 7, which are used jointly for one pixel BP, can be fulfilled only for discrete pixels BP, the spacing of the possible pixels BP depending on the distance of the micromirrors 4. Thus, the continuum of possible pixels BP in the image plane BE is restricted to the discrete grid of the diffraction orders of the micromirror array 3. The advantage of this embodiment, however, is that the amount of control data required for the micromirror array 3 and the mechanical complexity of the micromirror array is comparatively low.

According to a preferred embodiment of the invention, a length L of the micromirrors 4 and / or a width B of the micromirrors 4 is at least 5 times, preferably at least 10 times, and particularly preferably 20 times, the wavelength of the light beams LS. In this way it can be ensured that at the individual micromirrors 4 there is a deflection of the light beams LS according to the equation angle of incidence = angle of failure. In addition, the number of required micromirrors 4 can thus be kept low, so that the amount of control data required and the production costs for the micromirror array can be kept small

According to an advantageous development of the invention, the control device 2 is designed to form one of the micromirror groups 7 such that one of the micromirror groups 7 is formed from adjacent micromirrors 4 of the plurality of micromirrors 4. This makes it possible to ensure that the light beams incident on the micromirrors 4 of the micromirror group 7 thus formed are particularly coherent, so that particularly sharply delimited pixels BP can be generated. According to an advantageous embodiment of the invention which is not shown, the control device 2 can be designed in addition to controlling the micromirror groups 7 such that two adjacent pixels BP of the pixels BP can be generated by two non-adjacent micromirror groups 7 of the micromirror groups 7. As a result, it is possible that, in addition to the especially sharply delimited pixels BP, pixels BP with softer transitions can also be generated, since the coherence of the microspots on the microspots Gel 4 incident light beam LS decreases in practice, the micromirror groups 7 spatially objected. If partially coherent illumination is used, adjacent or overlapping pixels BP in the image plane BE may be formed by non-adjacent micromirror groups 7 whose spacing is above the spatial coherence length. Thus, in addition to the generation of particularly sharp pixels BP, it is possible to produce broader light distributions with softer transitions by selecting the light beams LS used to generate the one adjacent pixel BP to be incoherent with respect to the light beams LS used to generate - Be used the other adjacent pixel BP. FIG. 3 shows a diagram for illustrating the mode of operation of the first exemplary embodiment of the device 1 according to the invention.

FIG. 3 shows a one-dimensional simulation of the distribution of the radiation intensity SI.K in the image plane BE with superimposition of the coherent light bundles with the centroid rays SST1 to SST4 of the micromirrors 4.1 to 4.4 of the micropiping group 7.1 and for comparison the distribution of the radiation intensity SI in FIG the image plane BE with superposition of corresponding incoherent light bundles of 4 such micromirrors. It can be clearly seen that the radiation intensity SI.K reaches the four-fold maximum of the radiation intensity Sl.sub.1, the half-width falling to 1/4, so that a sharp and bright pixel BP is formed. However, such a distribution of the radiation intensity SI.K is possible only when the stroke of the micromirrors 4 is not adjustable, only at those discrete points at which an integer diffraction order of the grating of the micromirrors lies.

FIG. 4 shows a detailed view of a second exemplary embodiment of the device 1 according to the invention in a schematic representation. According to an advantageous development of the invention, the micromirrors 4 are additionally each by the control device 2 about a second axis ZA, which extends transversely to the first axis EA, tiltable, so that the direction of the centroid beam SST of the light beams LS reflected at the respective micromirrors 4 can be adjusted in two dimensions. In this way, the generated pixel can be positioned in the image plane in both the x and y directions.

In this case, the micromirrors 4.1, 4.2, 4.3, 4.4 of a first column of the micromirror array 3 can be tiltable about a first common second axis ZA1, but independently of one another, which is aligned parallel to the first column. The micromirrors 4.5, 4.6, 4.7, 4.8 of the second column can each be tilted independently of one another about a second common second axis ZA2; the micromirrors 4.9, 4.10, 4.11, 4.12 of the third column can be tilted independently of one another about a third common first axis ZA3 and the micromirrors 4.13, 4.14, 4.15, 4.16 of the fourth column can be tilted independently of one another about a fourth common second axis ZA4, wherein the second axes ZA1-ZA4 of the different columns can each be aligned parallel to one another.

According to an advantageous development of the invention, the control device 2 is designed to form one of the micromirror groups 7 such that one of the micromirror groups 7 is formed from two-dimensionally arranged micromirrors 7 of the plurality of micromirrors 7.

In this case, the micromirror group 7.1 can be formed from the micromirrors 4.1, 4.2, 4.5 and 4.6, which are arranged in the first or second column of the microphoto-array 3. The micromirror group 7.2 can be formed from the micromirrors 4.3, 4.4, 4.7 and 4.8, which are arranged in any case in the first or second column of the micromirror array 3; the micromirror group 7.3 can be formed from the micromirrors 4.9, 4.10, 4.13 and 4.14 , which are arranged in the third and fourth column of the micro mirror array 3, are formed, and the micromirror group 7.4 may consist of micromirrors 4.11, 4.12, 4.15 and 4.16, which are also arranged in the third and fourth column of the micromirror array 3, gebil - be det. FIG. 5 shows a detailed view of a third exemplary embodiment of the device 1 according to the invention in a schematic representation.

According to an advantageous development of the invention, the micromirrors 4 are each displaceable by the control device 2 along a stroke direction HR, which runs transversely to a mirror surface 8 of the respective micromirror 4, so that the optical path length of the light reflected at the respective micromirror 4 CG beam SST is changeable. If this feature is provided in the second exemplary embodiment, in which the micromirrors 4 can be tilted about the first axis EA and about the second axis ZA, then the pixels BP can be generated in the image plane BE as desired, that is to say without observing a grid Since the phase condition for each point of the image plane BE can be ensured by adjusting the stroke.

If this feature is provided in the first embodiment in which the micromirrors 4 are tiltable just about the first axis EA, then the pixels BP can be continuously generated on a line since the phase condition for each point of the line is adjusted by adjusting the Hubs can be guaranteed. In this case, in particular in applications which have different requirements for the two coordinate axes in the image plane BE, the outlay in the production and above all for the calibration and the activation of the micromirror array 3 can be reduced. From such an image line, a 2-dimensional image can again be generated by scanning transversely to its extent. This can be used particularly advantageous if z. B moves a workpiece to be machined on a conveyor belt on the exposure unit linearly over. See FIG. 10.

FIG. 6 shows a diagram for illustrating the mode of operation of the development of the third exemplary embodiment of the device 1 according to the invention. FIG. 6 shows a one-dimensional simulation of the distribution of the radiation intensity SI.K in the image plane BE with superimposition of the coherent Light beam with the centroid rays SST1 to SST4 of the micromirrors 4.1 to 4.4 of the micromirror group 7.1 and for comparison the distribution of the radiation intensity Sl.l in the image plane BE with superposition of corresponding incoherent bundles of four such micromirrors. The difference to FIG. 3 is that now the distribution of the radiation intensities SS.K and SS.I shown can be achieved by adjusting the stroke of the micromirrors 4 independently of the locations of the integer diffraction orders of the grating of the micromirrors.

FIG. 7 shows a partial view of a fourth exemplary embodiment of the device according to the invention in a schematic representation in an x-y plane. In this case, the micromirrors 4.1 and 4.2 form a first micromirror group 7.1. The centroid beam SST 1 of the micromirror 4.1 and the centroid beam SST 2 of the micromirror 4.2 are superimposed in the image plane BE, the pixel BP1 being formed. Furthermore, the center of gravity beam SST 3 of the micromirror 4.3, the center of gravity beam SST 4 of the micromirror 4.4 and the center of gravity beam SST 5 of the micromirror 4.5 are superposed in the image plane BE, so that the image point BP2 is created.

Since the pixel BP1 is generated by only two centroid rays SST1, SST2, while the pixel BP2 is of three centroid ray SST3 SST4, SST5, the maximum intensity of the pixel BP1 is less than the maximum intensity of the pixel BP2. For the same reason, the half width of the pixel BP1 is larger than the half width of the pixel BP2.

FIG. 8 shows a partial view of a fifth exemplary embodiment of the device according to the invention in a schematic representation in an xy plane. The fifth embodiment is similar to the fourth embodiment. In the fifth embodiment, however, the focusing device 6, seen in the direction of propagation of the light beams LS, is arranged in front of the micro mirror array 3. FIG. 9 shows a detailed view of a development of the second exemplary embodiment of the device 1 according to the invention in a schematic representation. According to an advantageous development of the invention, the control device 2 is designed to control a displacement device, which is designed to displace an irradiable region BB in a displacement direction VR relative to an object OB to be irradiated. An area which can be irradiated BB can be understood to be that area in which an optical pattern OM can be generated in one operation or with a single light pulse. The shape and size of the irradiable region BB are dependent on the degrees of freedom of the micromirrors 4, on the focal length of the focusing device 6 and on the possible deflection angles of the micromirrors 4. If areas outside the irradiable area are to be irradiated, this can be achieved by relative displacement of the object OB to be irradiated with respect to the irradiable area BB and by multiple light pulses, so that a larger total area BGB can be irradiated. This can also be referred to as stitching of optical sub-patterns. In the embodiment of FIG. 9, the irradiable region BB consists of a two-dimensional dot matrix with 20 possible pixels. Such a two-dimensional dot matrix can be produced with micromirrors 4, which can be tilted about two axes EA, ZA but can not be adjusted in the stroke direction HR. According to an advantageous development of the invention, the displacement device is designed as a mechanical displacement device. The mechanical displacement device can be designed such that either the optical pattern OM or the object OB to be irradiated or both are moved.

According to an advantageous development of the invention, the displacement device is designed as an optical displacement device. In this case, the optical displacement device can in particular have one or more tiltable mirrors and / or one or more rotating polygon mirrors. According to an advantageous embodiment of the invention, the displacement device VR is designed so that the displacement direction is oblique to a dot matrix of the optical pattern OM. As a result, even in those exemplary embodiments in which the micromirrors can only be tilted but are not movable in the stroke direction, so that pixels can only be generated on a discrete dot matrix, it is possible to use the dot matrix of possible pixels BP via the latter irradiating object OB to displace that the total irradiable area BGB completely covers the object OB to be irradiated.

FIG. 10 shows a detailed view of a further development of the third exemplary embodiment of the device according to the invention in a schematic representation. In the exemplary embodiment of FIG. 10, the irradiable region BB in the image plane BE consists of a lenticular continuum, possibly pixels. Since the displacement direction VR is provided transversely to the alignment of the linear continuum, the result is a quadrangular radiant total area BGB. A line-shaped continuous irradiable area BB can be produced, for example, with a micromirror array 3, in which the micromirrors 4 can be tilted only about an axis EA, but are also adjustable in the stroke direction HR.

FIG. 11 shows a detailed view of a development of the third exemplary embodiment of the device according to the invention in a schematic representation. In the exemplary embodiment of FIG. 11, the irradiable region BB in the image plane BE consists of a two-dimensional or rectangular continuum of possible pixels. A discrete shift of the irradiable area BB in the image plane BE and in the displacement direction VR results in an overall area BGB that can be irradiated which can be considerably larger than the irradiable area BB itself. A two-dimensional continuum of possible pixels can For example, be generated with a micromirror array 3, in which the micromirrors 4 about two axes EA and ZA tiltable and adjustable in the stroke direction HR.

FIG. 12 shows a detailed view of a development of the third exemplary embodiment of the device according to the invention in a schematic representation. In the embodiment of Figure 12 is the irradiable Area BB also from a two-dimensional continuum of possible Biidpunkte. In this case, the irradiable area BB is displaceable in the image plane BE both in a first displacement direction VR1 and in a second displacement direction VR2, so that the total radiationable area BGB widens a VR1 and VR2 in relation to the irradiable area BB in both displacement directions can be.

Aspects of the invention described herein in the context of the device according to the invention also represent aspects of the method according to the invention. Conversely, those aspects of the invention described herein in the context of the inventive method also represent aspects of the inventive device.

REFERENCE CHARACTERS:

1 Device for generating an optical pattern

2 control device

3 micromirror array

4 micromirrors

5 lighting device

6 focusing device

7 micromirror group

8 mirror surface OM optical pattern

BP pixel

BE picture level

LS beams

EA first axis

SST focal beam

STM control data for the micromirror array

STD control data for the lighting device

Sl radiation intensity

L length

B width

ZA second axis HR stroke direction

VR shift direction

OB to be irradiated

8B irradiable area

BGB total irradiable area

Sources:

[1] US 6,563,567 B1, Hideki Komatsuda et al., "Method and apparatus for illuminating a surface using a protection imaging apparatus";

[2] US 8,957,349 B2, Naoya Matsumoto, "Laser machining device and laser machining method";

[3] US 8,379,187 B2, Osamu Tanitsu, "Optical unit, illumination optical apparatus, exposure apparatus, and device manufacturing method".

Claims

Claims 1. Apparatus for generating an optical pattern (OM) from pixels (BP) in an image plane (BE), comprising: control means (2) for controlling the generation of the optical pattern (OM); a micromirror array (3) for reflecting light beams (LS) which are incident flatly on the micromirror array (3), the micromirror array (3) having a multiplicity of micromirrors (4), which are in each case at least circulated by the control device (2) a first axis (EA) can be tilted, so that a direction of a center of gravity beam (SST) of the light beams (LS) reflected at the respective micromirror (4) can be set; a lighting device (5) controllable by the control device (2) for generating the light beams (LS), which is designed such that the light beams (LS) are at least partially spatially coherent; a focusing device (6) for focusing the light beams (LS) reflected at the plurality of micromirrors (4) of the micromirror array (3) onto the image plane (BE); wherein the control device (2) is designed to control one or more micromirror groups (7) formed from a plurality of micromirrors (4) of the plurality of micromirrors (4) such that the micromirrors (4) of one of the micromirror groups (7) reflected

Focusing rays (SST) in the image plane (BE) meet and that optical path lengths of the at the micromirrors (4) of the respective micro mirror group (7) reflected focus beams (SST) of the lighting device (5) to the image plane (BE ) are equal or differ by an integer multiple of a wavelength of the light beams (LS) so as to produce a pixel (BP) of the pixels (BP).

2. Device according to the preceding claim, wherein a length (L) of the microrouges (4) and / or a width (B) of the micromirrors (4) is at least 5 times, preferably at least 10 times, and particularly preferably is 20 times the wavelength of light rays (LS).

3. Device according to one of the preceding claims, wherein the control device (2) for forming one of the micromirror groups (7) is formed, that one of the micromirror groups (7) from adjacent micromirrors (4) of the plurality of micromirrors (4) is.

4. Device according to one of the preceding claims, wherein the control device (2) for the purpose of controlling the micromirror groups (7) is such that two adjacent pixels (BP) of the pixels (BP) are separated by two non-adjacent micromirror groups (7). the micromirror groups (7) can be generated.

5. Device according to one of the preceding claims, wherein the control device (2) for controlling an intensity of the Beleuchtungseinrich- device (5) is formed.

6. Device according to one of the preceding claims, wherein the micro-mirror (4) in each case by the control device (2) additionally tiltable about a second axis (ZA) which is transverse to the first axis (EA), so the direction of the center of gravity beam (SST) of the light beams (LS) reflected at the respective micromirror (4) is two-dimensionally adjustable.

7. Device according to one of the preceding claims, wherein the control device (2) for forming one of the micromirror groups (7) is formed such that one of the micromirror groups (7) consists of two-dimensionally arranged micromirrors (7) of the plurality of micromirrors (FIG. 7) is formed.

8. Device according to one of the preceding claims, wherein the micromirror (4) in each case by the control device (2) along a stroke direction (HR), which transverse to a mirror surface (8) of the respective micro- Mirror (4) extends, are displaceable, so that the optical path length of the at the respective Mikrospiegei (4) reflected centroid beam (SST) is variable.

9. Device according to one of the preceding claims, wherein the control device (2) for controlling a displacement device is formed, which is designed for moving an irradiable area (BB) in a displacement direction (VR) relative to an object to be irradiated (OB) ,

10. Device according to one of the preceding claims, wherein the displacement device is designed as a mechanical displacement device.

11. Device according to one of the preceding claims, wherein the displacement device is designed as an optical displacement device.

12. Device according to one of the preceding claims, wherein the displacement device (VR) is formed so that the displacement direction is oblique to a dot matrix of the optical pattern (OM).

13. A method for generating an optical pattern (OM) from pixels (BP) in an image plane (BE), comprising the steps of: controlling the generation of the optical pattern (OM) by means of a control device (2);

Reflecting light beams (LS) which are incident flatly on a micromirror array (3), the micromirror array (3) having a multiplicity of micromirrors (4), which are each controlled by the control device

(2) are tilted at least about a first axis (EA) to adjust a direction of a centroid ray (SST) of the light beams (LS) reflected at the respective microspice (4); Generating the light beams (LS) by means of a lighting device (5) controlled by the control device (2), wherein the light beams len (LS) are generated such that they are at least partially spatially coherent;

Focusing the light beams (LS) reflected at the plurality of micromirrors (4) of the micromirror array (3) onto the image plane (BE) by means of a focusing device (6);

Use of the control device (2) for controlling a micromirror group (7) formed from a plurality of micromirrors (4) of the multiplicity of micromirrors (4) so that the centroid beams reflected at the micromirrors (4) of the micromirror group (7) ( 7) in the image plane (BE) and that optical path lengths of the centroid beams (SST) reflected at the micromirrors (4) of the micromirror group (7) from the illumination device (5) to the image plane (BE) are equal or even an integer multiple a wavelength of the light beams (LS), so as to generate a pixel (BP) of the pixels (BP).